Ah -- unfortunately I'm very ill-informed in regards to the last few quests of the main story, and didn't realize the marks aren't supposed to be there forever (though they do still seem to be present five years later, I think? Either Nald or Thal's is still present for Thancred to pray at in the new trailer).
Regardless, I'm still under the impression that the places chosen were not random. We see Nald and Thal's markings in the same place as their shrines in the city which they are the guardians of. Similarly, Nophica and Llymlaen have theirs in the cities which they protect. Halone's should be in Ishgard by that logic, but that's an obvious issue since it's not traversable by players, so we settle for having hers in Coerthas. ...So why not have Oschon's in the location of the city he once protected? You don't think his presence would be slightly stronger there?
Fair enough, and that was my mistake for making it sound like it was an indicator in and of itself. Instead, I just meant that it seems to add yet another small amount of credence to a theory that's already been gaining fast ground.